Evacuation of bulbs and the like



May 3 1927.

w. c. sPRoEssER EVACUATION 0F BULBS AND THE LIKE nunnualnnnueuounlasnnnbnlaocpa Filed Sept. 7, 1925 nnnnnlonnnuaonvann INVENTOR w/LL/m c. sPRoEssf/rz ATTORNEY 4Patented May 3, 1927.

' UNITED s'iarias'I PATENT oFFicE.- y

WILLIAM CHARLES SPROESSER, 0F .'BIQQOMFIELD, NEW JERSEY, ASSIGNOR TO WEST- INGHOUSE LAMP COMPANY, A CORPORATION 0F PENNSYLVANIA.

EVACITATION OF BULBS'AND THE LIKE.

Application sied september 7, 1923. seriai'm. 661,382.

This invention relates to the manufacture of evacuated devices and more particularly to the exhaustion of incandescent electric lamps and other vessels.

An object of-my invention is to manufacture evacuated devices in a simple and economical manner, avoiding the necessity of expensive vacuum pumps and like inachinery.

Another object of my invention is to provide means to obtain the desired degree of vacuum in incandescent electric lamps and 'i otheridevices by the use of readily vaporizable material which exerts no appreciable vapo pressure at ordinary room temperature A further object of my invention is to provide means for the evacuation vof bulbs and the like by ushing With the vapor of a material which is solid and exerts no appreciable vapor pressure at ordinary room temperatures and the subsequent removal ofA the vapor by condensation. j

A still further object of my invention 1s to create the desired degree of vacuum in incandescent electric lamps and other receptacles, by displacing the gaseous matter-Within vsuch articles by a condensible vapor which, under certain conditions, may have no appreciable vapor pressure.

Other objects and advantages of the 1nvention will become apparent upon reading the following description.

In order to obtain the requisite degree of vacuum in incandescent electric lainps. andother receptacles, it is necessary, according 'to processes in ordinary use, to employ expensive vacuum pumps and 'the exhaustion of such devices by such means is relatively slow.

According-to my invention, I make use of Y a method which is adapted to .eliminate theV use of rotary pumps in the exhaust operations and in fact may be extended to eliminate entirely the use of vacuum pumps of any description. This method may be called a physico-chemical process and consists essentially in creating the required degree of exhaust by the alternate vaporization and condensation of a volatile solid. Y

A preferred method of practicing my in- -vention may be briefly described as follows.

The lamp,-or other vessel to be evacuated, is connected to a bulb or ask containing a quantity of a solid substance which is prefs both vessels.

when heated to the desired temperature of exhaust, that is, Ato about 400 C. Its boiling point. should be at about the saine temperature or lower than that of the exhaust oven or, if using vacuum, it should have a vapor pressure approximating atmospheric at that temperature and its melting point should preferably, although not necessarily, be at a temperaturehigher than ordinary rooin temperatures.

The type of lamp or other vessel most suitable lfor evacuat'ing according to my iiivention is that of the tipless tipped variety or that in which an exhaust tube is provided extending through the flare tube or stein of the lamp and also a tubulature or exhaust tube is provided at the opposite en'd of the lamp bulb. The lamp bulb or other' vessel inay then be connected to the bulb or flask containing the material used for creating the desired vacuum, by either one of the exhaust tubes, leaving the remaining exhaust tube open tothe atmosphere or connected to an evacuating system or vacuum pump.

The lamp bulb or other vessel and t-he bulb or flask containing the Solid connected' thereto, may then be heated to the usual temperature ot' exhaust, preferably in an oven, thereby causing the solid to vaporize at least in part and displace the air in both vessels so that the same are completely filled with the vaporized solid which will then start to either escape from the free exhaust tube* or be drawn into the evacuating system connected to said exhaust tube. At this point, the lamp or the like may be either tipped ott' at the free exhaust tube or that one connected to the evaciiating system or at least, temporarily sealed/fatY that point.

The bulb or flask containing the solid ma-lv terial used for the exhausting purpose, is then either cooled or allowed to cool While maintaining the lamp i'n its heated condition. This causes the 'vaporizedsolid in the bulb or ask to recondense and solidify thereby causing the vapor 'in the heated Alamp to How to the cooleV ask and be there i'condensed leaving an excellent vacuum in taining the solid has been cooled to, cause the condensation of substantially all the vaporized material in the vessels, the lamp .ico

Whenthe bulb or flask coni may then be tipped oi at the exhaust tube between it and the flask and withdrawn from the oven to allow it to cool. Then, if not already permanently tipped off at the other exhaust tube, this may be done and it will be found that an excellent vacuum has been created therein. y

It will be apparent that the use of a vacuum pump or other mechanical exhausting means is unnecessary, but may be employed if desired to expedite the process. Although a vesselor lamp with two exhaust tubes is preferably employed, so that the vapor eau be admitted at one tube and allowed to flow .out ot the other, yet my methods applicable lo lamps or vessels hair` ing only one exhaust tube, as they may be Vrepeatedly ilushed and exhausted to eliminate substantially all the original air therein. That is, the vessel maybe heated, eX- hausted and filled with the vapor of the substance used. again exhausted and refilled withlthe vapor and the' process repeated until a negligible and harmless amount of air remains. The bulb or flask containing the substance used for the exhaust process may then be cooled, as heretofore, While maintaining the lamp or other vessel hot and a good vacuum created in the lamp bulb in the same manner as heretofore described.

My invention will better be understood by the following' more detailed description taken, in connection with the accompanying drawing, the single figure of kwhich killustrates a preferred apparatus for practicing my invention, shown in side elevation, partly inwsection.

' A conventional form of incandescent electric lamp 1 of the vacuum type is illustrated, but it isiobvious that my method of exhaust is applicable for the evacuation of any receptacle. The lamp 1 illustrated, is shown provided witha mount 2 suppliedwith an exhaust tube 3 connected to the interior of a -bulb thereotI at 4. In other words, the mount 2 is a tipless type of mount, in that the lamp may be evacuated thereby through an exhaust'tube therein and the usual tip on the other end of the bulb avoided. For the purposes of myy invention, however, it is preferable that another exhaust tube 5 be pro.-

A' vided, although the same is not essential.

The exhaust tube 5 may be connected inany desired manner, .for example, rubber tubing connector 6 to means such as a stopcock 7. for sealing thel same from the at-y mosphere or from an evacuated system or pump (not shown) to which said exhaust tube 5 may be connected to, through stop-1 cock 71 The lamp 1 is connected by one of its exhaust tubes to a bulb or ilask 8, containing a -quantity 'of a vaporizable solid 9. In this instance, it is Vshown connected toexhaust tube 3, but it is immaterial which tube is z The characteristics oi' the solid 9 used in t 'the exhaust operation are that, l(l) it should preferably have no appreciable vapor pressure at ordinary Vroom temperatures, (2) its t vopor must be stable when heated to the desired temperature of exhaust, that is, to about 400 C. or not higher than 500 C'., (3) its boiling point should be at about the same temperature as thatof the exhaust oven, that is, about 400 C. or less (4) its melting point should preferably be at a tem perature considerably above ordinary room temperatures, althoughv this is notas essential. as its vaporization characteristics, (5) it should preferably be white in color, (6) it should be relatively inexpensive and (7) which should have no detrimental elect on the filament.

The following halide salts have properties which make them acceptable for use.

- Meltin Boiling Compound. l pointe point Q Alan l 93 263 Alf- Sublimes. 183 All. 185 360 sbBr. a; am

An o'ven 12 is provided with an opening 13 through which the exhaust tube 5 passes and lower doors 14 through which the lamp 1 and the flask 8 may be inserted or removed. Heating means of any preferred form may be provided for said oven and as shown, may comprise resistance wire 15 heated fromany vdesired source of electricity (not shown) to provide the desired temperature in the furnace. An electric fan 16 may be provided, if desired, for cooling the llask 8 after removing' the same from the furnace. 3

The operation of theapparatus heretofore described for practicing 'my invention may 'be as follows: The lamp 1 and its connected Alask 8 containing a. quantity of the solid 9 is enclosed and held in posit'on in the Oven `12in any desired manner, as by means of exhaust tube 5 and the stop-cock 6 is' left Aopen to the atmosphereor to a vacuum pump or other evacuating system, as naybe desired. The resistance wire 15 is energized from a suitable source of electricity (not shown) to cause the lamp 1 and the ilask 8 to be heated to aboutr400 C., thereby sufficiently baking out the lamp and vaporizing' or be cooled by any preferred means, as forN example, the electric fan 16. As the flask 8 cools, the vapor therein condenses to its original solid form, thereby 'producing a partial vacuum and causing the vapor in the lamp 1 to flowback to the flask 8 throughv the exhaust-tube 3 and neck 10.

When the flask 8 has been cooled to its original room temperature, all vapor in both the lamp 1 and flask 8 will be recondensed in the flask 8, thereby producing a good vacuum in both of said vessels. The lamp may then be tipped off as usual at the exhaust'tube 3 and if not already permanently sealed at the exhaust tube 5, this may then be done to produce a lamp of tlievacuum type, with avery high degree of vacuum therein.

It should be noted that aluminum bromide n or the other halide salts mentioned are candle power maintenancematerials, that is, when deposited on the bulbin thin laye-rs they prevent to a large degree, blackening ofthe bulb by the deposition of -vaporized filamentary material. Therefore, should trating preferred apparatus, it is tovbe understood that lamps or other vessels comprising only. one, as well as two exhaust tubes, may be exhausted as described without departing fromthe spirit and yscope of my invention, as'it will be readily appreciated that the air in such lamps or the like may be removed by alternately evacuating'the' lamp and flushing with the vapor of the solid used until the air is eliminated a preferred therein to any desired degree, after which the vapor may be recondensed in the vessel supplying the same as heretofore described. The use of a vacuum pump or other mechanical exhaust means is unnecessary with apparatus such as illustrated in the drawing,^when exhausting lamps 0r the like provided with two exhaust tubes. However, when exhausting lamps or other vessels provided with only one exhaust tube, it is desirable to have some means for preliminarily exhausting the same, in connection with the flushing thereof with the desired vaporized material.

What is claimed is:

1. A materialfor the evacuation of a gastight enclosurexby displacement of the air therein comprising av vaporizable halide salt having no appreciable vapor pressure at room temperature and capable on condensation of leaving a first class vacuum. in said enclosure. f

2. A material for the evacuation of a gastight enclosure containing an incandescible filament, comprising a vaporizable halide salt capable on vaporization of displacing the air within said enclosure and on condensationfof creating a first class vacuum therein, said material exerting no harmful effects on said incandescible filament.

3. A material for'the evacuation of a gas- 'tight envelope, by displacement of the air therein, comprising aluminum bromide, said material on condensation leaving a first class vacuum within the envelope.

4. Amaterial .for the evacuation of ineandescent electric lamps comprising a halide salt capable on vaporization of displacing the air within the lamp and on condensation of leaving a first class vacuum in the lamp, said material exerting no harmful effectson the filament and assisting by condensation on the envelope, of maintaining the candle power of the lamp.

In testimony whereof, I have hereunto subscribed my name this 6th day of Sept/ember, 1923.

WILLIAM'CHARLES srRoEssER. 

